The invention relates to an intake device for an internal combustion engine, to which at least combustion air and an additional fluid can be supplied via an air inlet line.
EP 0 507 996 A2 has disclosed a device for the metered feeding of burnt gases into the combustion space of an internal combustion engine. A line branches off from an exhaust pipe of the internal combustion engine, the recirculated exhaust gas being supplied under the control of a valve to an intake pipe and then being involved in the process of combustion in the internal combustion engine. This prior art does not provide any details on the connection of the feed line to the intake pipe.
The object on which the invention is based is to provide an intake device for an internal combustion engine which is distinguished by simplicity of design and very good efficiency.
The presence of an opening through which a guide tube projects into the air inlet line in accordance with the invention has the advantage that it is possible to use as a guide tube a simple and therefore economical piece of tube which is inserted through the opening into the air inlet line and fixed in a loss-proof manner. The introduction of an opening as a hole is a simple production process, it being necessary to allow for this hole during the production of the air inlet line rather than having to make it subsequently. The fact that the guide tube projects into the air inlet lines provides the advantage that high wall temperatures of the air inlet line are avoided, and the additional fluid supplied is fed into the main flow passing through the air inlet line. It also avoids excessive temperatures in the region where the additional fluid is fed in (if this region is manufactured from metal) from leading to impermissible heating or even destruction of flanged-on lines, especially when these are manufactured from plastic. Large differences in temperature, which lead to fatigue of the materials, are thus also avoided. The additional fluid which can be fed in is, for example, recirculated exhaust gas, but it could also be fresh air, a fuel/air mixture or turbulent fuel.
As a development of the invention, the air inlet line has a throttle body with a throttle valve, the hole with the guide tube being arranged in the region of the throttle body. This throttle body, which, in a manner known per se, has a drivable throttle valve for varying the power output of the internal combustion engine, thus forms a modular unit in which the hole for receiving the guide tube is provided. This has the advantage that the throttle body can be preassembled as a unit, on which it is then only necessary to produce the air feed, e.g. from an air filter, and the connection to the intake region of the internal combustion engine.
As a development of the invention, the air inlet line or the throttle body has a flange for the attachment of a valve for the supply of the additional fluid, the hole with the guide tube being arranged in the region of the flange. This has the advantage that the valve (e.g. an exhaust-gas recirculation valve) can be fixed directly on the air inlet line or the throttle body, thus ensuring a compact construction. The valve can, of course, also be arranged at another location, in which case the flange is used for the attachment of a feed line for the additional fluid.
As a development of the invention, the air inlet line or the flange can be connected firmly to the guide tube. This ensures that the guide tube is fixed in a loss-proof manner since, if it falls into the air inlet line, it can lead to damage, possibly even destructive damage, to the internal combustion engine. The firm connection can advantageously be achieved by means of a pressing operation since, particularly when taking into account the high temperatures which occur in exhaust-gas recirculation, it can be implemented in a simple manner. Other fixing processes, such as welding, adhesive bonding or the like, are also conceivable, and not only force-locking connections but also form-locking connections which, in particular, meet the temperature requirements, should be taken into account.
As a development of the invention, an at least partially encircling groove, into which one end region of the guide tube can be pressed, is provided in the air inlet line or in the flange, in the region of the hole. This ensures not only security against loss but also a sealing effect and good feeding in of the additional fluid in a manner which is favorable in terms of flow. Another advantage is that involved machining of the guide tube is not necessary, making it possible to use a commercially available piece of tube. It is likewise advantageous that involved machining (e.g. finishing turning) of the sealing surface of the flange is eliminated.
As a development of the invention, the guide tube can be inserted into the hole and has means, in particular a encircling collar, by means of which the guide tube can be held in a nominal position. This has the advantage that no further machining steps are required in the region of the hole to install the guide tube. It is simply inserted into the hole until the collar comes to rest against the sealing surface of the flange (or the surface of the air guide tube), thus giving not only simplicity of installation but, once again, a high degree of security against loss. The use of an installation tool is not necessary since the guide tube is fixed in its nominal position once the valve or another feed line has been attached to the flange.
As a development of the invention, in one end region, by which it projects into the air inlet line, the guide tube has a flattened portion. This has the advantage that the guide tube can be inserted more quickly and in a more simple manner into the hole since constrained guidance is provided owing to the flattened portion. A flattened portion of this kind is advantageous particularly when the diameters of the hole and of the guide tube are very largely the same. On the other hand, a flattened portion of this kind can be omitted or used nevertheless if the diameter of the air guide tube is significantly less than the diameter of the hole, in which case it should be ensured that the means by which the guide tube can be held in its nominal position are of appropriate design (particularly that their diameters are chosen to be greater than the diameter of the hole) in order to ensure the security against loss.
As a development of the invention, in its other end region, which points in the direction of the valve, the guide tube has a triangular shape. By virtue of this triangular shape in one end region of the guide tube, an additional prestress is produced in the holding region, in particular in the region of the encircling groove, to ensure that the guide tube fits tightly.
As a development of the invention, the guide tube is arranged on the valve or is part of the valve. In this alternative configuration, it is possible to combine security against loss with accurately targeted feeding of the additional fluid into the air inlet line in order to avoid impermissibly high wall temperatures of the air inlet line in the region of introduction. Moreover, simplicity of installation is increased since, in this configuration, the guide tube and the valve form a modular unit and thus only the valve, in particular its housing, has to be fixed on the air inlet line.
As a development of the invention, the additional fluid is the exhaust gas from an internal combustion engine, the valve being provided as an exhaust-gas recirculation valve in particular as a controllable valve. Exhaust-gas recirculation valves are known per se and used to increase the efficiency of the internal combustion engine, and it is therefore not necessary to refer further here to their advantages. The use of the guide tube is particularly advantageous when the exhaust gas from the internal combustion engine is recirculated as the additional fluid since, in this case, high temperatures are present, which can lead to impermissibly high wall temperatures and to fatigue of the materials due to high temperature fluctuations in the region of introduction and at the flange (throttle body of metal, flanged-on lines made of plastic), these temperatures being avoided in an effective manner by the use of the guide tube, which directs the exhaust gases into the central area of the air inlet line.
Owing to the configuration of the air inlet line, it seems appropriate to provide the air inlet line subsequently with an opening, in particular the hole already mentioned, and to introduce the guide tube into this. Also conceivable are production methods in which at least one guide tube (xe2x80x9cstubxe2x80x9d), which projects into the air inlet line, is provided. The same applies, for example, to aluminum diecasting methods for the production of throttle bodies. As a supplementary measure to this, the flange for the valve can also be provided at as early a stage as the production of the air inlet line, especially when the latter is cast.
In addition to feeding in exhaust gas as the additional fluid, as described, it is, of course, also possible to feed in other gases (e.g. fresh air or a fuel/air mixture) or to feed in fuel in a controlled manner. The preferred areas of application are spark-ignition and diesel internal combustion engines.